Searchlight control system



Nov. 9, 1948. D. A. YOUNGSON ETAL 2,453,175

SEARCHLIGHT CONTROL SYSTEM Filed Sept. 25, 1946 Inventors:bonaldAYouncgso RObeTtEMattheWs by www Their/ ttorney Patented Nov. 9,1948 UNITED STATES PATENT YGFFICE SEARCHLIGHT CONTROL SYSTEM ApplicationSeptember 25, 1946, Serial No. 699,250

7 Claims.

"Our invention relates to light projectors of the arcing-electrode type,and more particularly to control systems for are searchlights and thelike. The invention is especially applicable to searchlights whereinquick starting or are initiation is 'desired, as in searchlights used onaircraft or for aircraft observation.

In the operation of are light projectors it is customary to' advance thenegative electrode until it makes contact with the positive electrode,andthereupon to withdraw the negative electrode to strike the arc. 'Timemay be saved in this operation if the electrodes are brought intoengagement immediately upon extinguishing the arc and allowed to remainin engage ment until the next are striking operation. Arc striking thenis accomplished simply by withdrawing the negative electrode.

Accordingly it is a general object of our invention to provide new andnovel control means for arc lightprojectors.

It is a further object of our invention to provide a low voltage quickstarting electrode feed circuit for are light projectors which isentirely independent of the normal high voltage source ofarc currentsupply.

'It is a more particular object of our invention to provide new andnovel mean for automatically-engaging the electrodes of an are lightprojector immediately upon deenergization of the energized during arcingoperation from a low voltage source of electric current supply. In orderto move the electrodes into engagement immediately upon extinguishmentof the arc to prepare the'projector for quick starting operation, weprovide switching means operable to connect the low voltagecurrentsupply source to the electrode feed motor through an alternative circuitwhenthearc currentsupply .is disconnected. During .such connection ofthe ,feed

motor, the low voltage source is'also connected 4 to the'electrodes inorder to. detect engagement thereof and thereupon to disconnect the feedmotor.

Forv a. more. complete .under'standing or our invention,reierenceshouldmow behad tothe fol lowing detailed specification alongwith theacline"!, through a cut-out switch 8, a-selector switch 9, and apair of normally closed contacts ii) of a relay II. The switch! closeson a stationary contact l2 in its operating position and on a stationarycontact l3 in its standby position.

The negative electrode 2 is supported by a pair of driving rollers 1 i5and a pair of spring pressed electric conducting guide brushes l6, l1.Current is supplied to the electrode 2 through the brushes H5, H, asshown, and the roller 15 is serrated and driven by a negative drivemotor 18, thereby to advance or retract the electrode 2. The drive motor18 is provided with a normally engaged magnetic'brake l9 and a pair ofoppositely wound series field windings 2i! and 2 l. The magnetic brakei8 is arranged to be disengaged upon energization of the motor I8 by abrake coil 22 connected in series circuit relation in the motor circuit.The series field'windings 20 and 2t are arranged to be alternativelyconnected to the source of control power 'I through the switches Band -9and a current regulator 23. The regulator 23 comprises a currentresponsive actuating winding 24, a pair of normally closed contacts 25and a pair of normally open contacts 26. The winding 24 is connected inseries circuit relation in the arc circuit of the electrodes I and 2."The contacts 25 and 25 are controlled by abridging contact" 21. Themotor 18.. when energized through the series field winding 2i, isarranged to drivelthe electrodfe'2 in-a forward direction towardtheelectrode l. The motor fieldwinding 20, when energized, causes the motori8 t o operate in the opposite direction, thereby to retract theelectrode 2. The field Winding 2i is energized through the regulatorcontacts 26 only when the current through thearc and thus through theregulator coil 2% exceeds a. predetermined maximum value.

Thepositive electrode l is arranged for con tinuous rotation and forwardfeed alternatively 3 at one or the other of two selectable speeds. Forthis purpose the electrode l is mounted in a 1'0- tatable head 28 whichis journaled in a fixed sup port 29. The head 23 comprises a hollowsleeve 38 within which the electrode is slidable loosely. The sleeve 35carries at one end a gear bracket 3i. Within the gear bracket 3! theelectrode i is supported between a guide roller 32 and a serrated ortoothed driving roller The electrode l is further guided and alsosupplied with current by a pair of spring pressed electric conductingsliders 34 and 35. The shaft of the driving roller 33 carries also adriving pinion 36. The pinion 35 meshes with a worm gear 31 journaled at38 in the rotatable head bracket 3|. The shaft of the worm gear 31carries at its opposite end a planetary spur gear 39 which meshes with asun gear 48 journaled in the frame 29 and rotatable with respect to theelectrode head 28. Specifically the sun gear 40 is attached to arotatable hollow sleeve 4| which is journaled in the frame 29. On thesleeve 4! adjacent the pinion 45 there is mounted a spur gear 42. Thehollow sleeve 38 forming part of the rotatable head 28 is rotatablyjournaled within the sleeve 4!. At the end of the sleeve 313 remote fromthe gear bracket 3i there is mounted a spur gear 43 fixed to the sleeve30 by a setscrew 44. The spur gear 43 is of slightly greater diametethan the spur gear 42. Finally, the gears 42 and 43 are simultaneouslyand continuously driven by a pair of pinions 45 and 46. The pinions 45and 46 are journalled in the frame 29 and connected, as by a shaft 41(indicated schematically), to a driving motor 43. The pinion 46 isslightly smaller than the pinion 45, so that the spur gear 42 is drivenfaster than the gear 43. It will of course be understood that, ifdesired, the gear .42 may be driven slightly slower than the gear 43, itbeing only necessary that the gears 42 and 43 be driven at unequalspeeds. It ma be noted however, that if the speed relationship isreversed from that shown, it is also necessary to reverse the directionof rotation of the motor 48 so that the electrode I will advance.

It will be observed that in the operation of the positive electrodedriving mechanism, the spur gea 43 driven by the motor 48 and attachedto the electrode head 28 rotates the electrode head about its own axis,thereby continuously to rotate the electrode i. If, now, the spur gear42 were not driven, but were allowed to rotate idly upon the sleeve 36,it would be carried around by the supporting head 28 and the gears 36,37 and 39 at the same speed as the head, so that the gears 31 and 39would not rotate upon their own axis and therefore would not drive theelectrode 1 longitudinally. In fact however the spur gear 42 ispositively driven by the pinion 45 at a speed slightly greater than thespeed of the head 28 itself. Thus, the planetary gear 39 is caused toroll slowly around the sungear 40, thereby to rotate the worm gear 37ondits own axis and continuously to drive the .positive electrode iforward as it rotates. As will bfe explained more fully hereinafter, thecrater'in the end of the positive electrode is maintained in a predetermined desired position providing two solectable driving speeds forthe positive head mechanism in conjunction with a control systemresponsive to crater position, as described and claimed in copendingapplication Serial Num ber 699,287, filed September 25, 1946, by RobertC. Sheahan, and having the same assignee as this application, whichhaspbecome U. S. Pat

ent 2,440,122, dated April 20, 1948..

During normal arcing operation, the positive driving motor 48 isconnected to the low voltage source of control power 7 through themanually operable cut out switch 3 and the selector switch 9. The motor48 is provided with a shut field winding 49. For control of the speed ofthe mo-- tor 48 there connected in series with the motor armature avariable resistor which is arranged to be shunted b a thermallyresponsive switch 5|. The switch 5| is closed when cold, and opens itscontacts when hot to insert the resistor 5il in the motor armaturecircuit.

The thermally responsive switch 5|, and thus the speed of the motor 48,is controlled in accordance with the position of the crater in the endof the electrode 5. This control may conveniently be effected by anywell known optical system, such as that described. in U. S. Patent1,590,543, issued on June 29, 1926, to Martin L. Patterson, and entitledFeed control means for are lights. Briefly such a system comprises anoptical arrangement for reflecting the image of the positive craterdirectly upon the thermal responsive member 5| when the crater is in thedesired position. In this position of the crater, then, the switch 5! isheld open and the motor 48 operates at its low speed. If, however, thecrater burns back farther than desired, the image of the crater movesoil of the thermal responsive member 5|, the member 5| closes itscontact, and the speed of the motor 48 is increased, thereby to drivethe electrode I forward at a greater speed.

As previously stated, means are provided for driving the electrodes land 2 into contact immediately upon deenergization of the are betweenthe electrodes, thereby to prepare for the next are striking operation.For this purpose, means are provided for connecting the electrodedriving motors l8 and 4'8 to the low voltage source of control power llthrough alternative circuits when the selector switch 9 is in itsstandby position on the contact l3. In this position of the selectorswitch a circuit is also completed for applying control potential fromthe source 7! to the electrodes and 2 so that, when the electrodes comeinto contact, a driving motor disabling circuit is completed.

Referring more particularly to the drawing, it will be observed that,when the selector switch 9 is in its stand-by position on the contactI3, a circuit is completed through the switches 8 and 9 from the controlpower source I to an actuating winding 52 of the relay l l. In parallelcircuit relation with the winding 52 there is also a green indicatinglamp 53 which is lighted in the stand-by position of the switch 9. It isdesirable to provide also a red indicating lamp 54 which is lighted fromthe control power source 1 so long as the cutout switch 8 is closed.Thus, the lamp 54 onl is lighted during arcing operation, while thelamps 53 and 54 are lighted in the stand-by condition.

When the relay i l picks up, it first opens its contact iii, thereby'todeenergize the contactor actuatin winding 5 and to ensure dropout of thehigh voltage line contactor 4. Thus, disconnection of the high voltagegenerator 5 from the electrodes during stand-by or quick startingoperation is assured. Upon energization, the relay H also closes threepairs of normally open contacts 55, 56, and 51. The contacts 55, whenclosed, complete an alternative energizing circuit for the drivingmotors it! and 48. This cir cuit may be followed from the control powersource l through the cutout 8,-the selector romance 'sw-itchfi'in"itsL'stand-by position, a normally closed contact58 ofa relay58,.and the relay -contact' 55 to the" driving motors in parallel' circuitrelation. The relay contacts 56 and 5?. when r closed prepareanrenergizing circuit for anzac- 'tuating/winding 8i) of therelay 59through the electrodes I'. and.2. This circuit'mayrbe followed from thesource of control power I. throughithe cutout switch 8; the selectorswitch 9 in its standby.-'.position,: the'relaycontacts 57, theelectrode Lathe: electrode 2,1the relay contacts56, and. the actuatingwinding: 69: of the relay. 59.:back to the. control powersource I. .Thislatter-circuit, ofrcourse, isxnot-completed until the electrodes hand 2come into'engagement.

With the foregoing description of" the various elements of our systemand their individual mode of operation, the operation oftheisystem asauwhole will now be: readily'understood' from the following brief:description.

.To consider first normal arcing operation,,.let .it be. assumed thatthe electrodes are separated tas illustrated; and that the cutout switch8 is closed and'the selector switch-9 placed in its operating positionon the contact I2. With the -.switch8 closed thezred indicatin light 54.is energized. Through the sWitchrB and the con- ..tact I2 of'the switchil circuits are completed for thetdriving motors Hand 48 in the 'mannerpreviously described, the circuit for" the negative drive motor I8passing through the bridg- .ing contact 2! of-the. regulating relay- 23.In parallel circuit relation with :the motors, there is also completedanenergizing circuit for the actuating winding 6 of the'line contactor4. This energizing circuit includes the normally closed contact Ill ofthe relay II. Accordingly, therefore, as soon as the switch 8 is closedand the "switch '9 placed in its operation position, the driving motorsI8 and 48 are placed in operation and theline contactor 4 is picked upto apply arcing voltage to the..electrodes from the generator. 5.

..Since.no arc exists, the regulator contacts are closed and thenegative driving motor drives the electrode 2 forward into engagementwith the electrode I. The electrode I, of course, is simultaneouslybeing driven forward at its maximum speed because the thermal responsivemember 5I is cold. When the electrodes I and 2 come into contact, theresulting high current flow picks up the regulating relay 23, openingcontacts 25 and closing contacts 26, thereby reversing operation ofdrive motor I8, which withdraws electrode 2 from contact causing an arcto be struck between I and 2. With arcing taking place, the crater atthe end of the positive electrode I is maintained in a predeterminedposition by operation of the thermal responsive member 5| and the motor48, and the negative electrode 2 is advanced or retracted as required inorder to maintain the arc current substantially constant.

When it is desired to extinguish the arc, the selector switch 8 is movedfrom its operating position on the contact I2 to its stand-by posi tionon the contact I3. As soon as the contact I2 is disengaged, the normaloperating circuit for the driving motors I8 and 48 is disabled and theactuating winding 6 of the high voltage line contactor 4 is deenergized.However, as soon as the selector switch 9 is placed upon the standbycontact 53, an energizing circuit is completed for the actuating winding52 of the relay II. When the relay II picks up, a new energizingcircuitis completed for both electrode driving motors I8 andthrough'the' contact sacrum relay' 59 and the contact 55 of'the relay-II. JSi- :multaneously, controlpotential is applied tothe electrodes Iand 2 through the actuating wind- 'ing'fifl' of the'r'elay'59 and thecontacts 56 and 5! o? therelay II asheretoiore described. Accordingly,therefore, both electrodes are advanced until they come intoengagement.-As soon. as the electrodes I and 2 are engagedya circuit is completedthrough the electrodes for the actuatingwindinglfiil of the relay 58."When the'relay 59 is pickedup, it opens itscontact-SB therebytold'eenergize'both driving motors I8 and =48. '.Thus, int-he stand-byposition, the-"electrodes I. and 2 remain in engagement and the relaysII andJSB'remain picked up, the relay 59 being energized from the lowvoltage control power. source through the electrodes I and 2 themselves.Both indicating lamps 53 and are lighted to indicate this condition.

It shouldrbe'n'oted that, if desired, thegreen lamp 53 may b'e-soconnected that'it will'ubeli'ghtedsonly when the electrodes I and 2actually-engage. If suchindication isdesired it is onlycnecessary-toconnect the lamp 53 in serieswith the relay contacts 58, rather than asshown. I Itwill now he appreciated'that in: our new and improved system"resetting of the. electrodes for quick starting operation iss'carri-ed'z out entirely at low voltage so that the. system'is entirelysafe and free from dange of reinitiating the are at undesired times.Disabling of the high voltage "circuit is ensured b the selectorswitchls, which, whenpla'ced in the reset position removes high voltagepower from the electrodes.

While we have shown and described only -a preferred embodiment of ourinvention 'by Way of illustration, many;rnodifications "will OCCLll" tothose skilled in the art and wetherefore wish to haveit understood thatwe intend in the appended claims to cover all suchmodifications as fallwithin the true spirit and scope of our. invention.

. -What we claimzasnew and'desire'tosecure by Letters-Patent of theUnited States. is:

1. In a light projector including a pair of arcing electrodes, means forconnecting said electrodes to and disconnectin said electrodes from asource of high voltage electric current supply, electrode feed controlmeans including an electric motor, means for connecting said motor to asource of low voltage electric current supply and simultaneouslyapplying the potential of said low voltage source to said electrodeswhen said high voltage source is disconnected, said motor when soconnected driving said electrodes toward engagement, and electricalmeans responsive to completion of a low voltage circuit by engagement ofsaid electrodes for deenergizin said mo-,

tor.

2. Inv a light projector including a pair of arcing electrodes,electrode feed control means including an electric motor, means forsimultaneously connecting said electrodes to a source of high voltageelectric current supply and connecting said motor to a source of lowvoltage electric current supply, separate means operable when said highvoltage source is disconnected for connecting said motor to said lowvoltage source, and relay means operable from said low voltage sourceupon engagement of said electrodes to disconnect said motor from saidlow voltage source.

3. In a light projector including a pair of arcing electrodes, electrodefeed control means including an electric motor, switching means forsimultaneously connecting said electrodes to a source of high voltageelectric current supply and connecting said motor to a source of lowvoltage electric current supply, relay means operable by said switchingmeans for connecting said motor to said low voltage source when saidhigh voltage source is disconnected, and second relay means operativeupon engagement of said electrodes when said first relay means isoperated for disconnecting said motor from said low voltage source.

4. In a light projector includin a pair of arcing electrodes, electrodefeed control means including an electric motor connected to drive one ofsaid electrodes toward engagement with the other, first switching meansfor connecting said electrodes to a source of high voltage electriccurrent supply and simultaneously connecting said motor to a source oflow voltage electric current supply to energize said. motor, secondswitching means operable only when said first switching means isinoperative for connecting said motor to said low voltage source withsaid high voltage source disconnected and simultaneously applying saidlow source voltage between said electrodes,

and electro--responsive means operable from said low voltage source uponengagement of said electrodes to disable said second switching meansthereby to deenergize said motor with said electrodes in engagement.

5. In a light projector including a pair of arcing electrodes, means forconnecting said electrodes to a source of high voltage electric currentsupply, electrode feed control means including an electric motorconnected to drive one of said electrodes toward engagement with theother,

means for connecting said motor to a source of low voltage electriccurrent supply to energize said motor, and means responsive toengagement of said electrodes for rendering said low voltage connectingmeans inefiective, thereby to deenergize said motor with said electrodesin engagement.

6. In a light projector including a pair of arcing electrodes, means forconnecting said electrodes to a source of high voltage electric currentsupply thereby to maintain an are between said electrodes, electrodefeed control means including a reversible electric motor connected todrive one of said electrodes toward and away from the other, means forconnecting said motor to a source of low voltage electric current supplyto energize said motor, regulating means responsive to are current forcontrolling said motor to maintain said current substantially constant,said regulating means controlling said motor to drive said electrodestoward engagement when said high voltage source is disconnected and saidare extinguished, and mean responsive to engagement of said electrodesfor rendering said low voltage connecting means ineffective thereby todeenergize said motor with said electrodes in engagement.

7. In a light projector including a pair of arcing electrodes, means forconnecting said electrodes to a source of high voltage electric currentsupply, electrode feed control means including an electric motorconnected to drive one of said electrodes toward engagement with theother, first switching means for connecting said motor to a source oflow voltage electric current supply when said are is operative, secondswitching means for connecting said motor to said low volt age supplysource when said are is inoperative, and means responsive to engagementof said electrodes for disabling said second switching means, thereby todeenergize said motor with said electrodes in engagement DONALD A.YOUNGSON. ROBERT E. MATTHEWS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,701,372 Jefts Feb. 5, 19291,976,551 Frich Oct. 9, 1934

